BEA Airtours had the 2 letter flight prefix KT, or Kilo-Tango. c/s was 'Beatours'.
Operated Comets and ex-BOAC 707-436s.
I think it became British Airtours after the merger, using 707s, 737s, L1011s and 747s. It still used KT, and Beatours, as far as I remember.